Prophylaxis against hypomagnesaemia induced by cis-platinum combination chemotherapy.

Hypomagnesaemia is recognised as a feature of the renal tubular defect produced by cis-platinum therapy for cancer. It may be sufficiently severe to cause tetany and grand mal fits. Attempts to correct established hypomagnesaemia whilst continuing cis-platinum therapy have not proved satisfactory. We have therefore investigated the prophylactic addition of 3 g magnesium sulphate to the high-dose platinum regimen with which metastatic malignant teratoma is treated in this unit. Serum magnesium levels have been measured in eight patients treated in this way and compared with those recorded for eight matched patients previously treated without routine magnesium supplements. Magnesium levels fell into the range frequently associated with clinical manifestation in five of the eight unsupplemented patients and only one of those given magnesium prophylactically. Mean serum magnesium levels were significantly higher in the supplemented group when compared using the paired t-test (P less than 0.01). Routine supplementation with intravenous magnesium sulphate is a simple and effective way of preventing symptomatic hypomagnesaemia associated with cis-platinum therapy.